Catalyst finned tubing and method of making



CATALYST. FINNED TUBING AND METHOD OF MAKING Filed March 11, 1953 Jan. 22, 1957 E. BRUEGGER 2 Sheets-Sheet 1 F1410 INVENTOR.

Ernsi' Brueyger ATTORNEYS CATALYST FINNED TUBING AND METHOD OF MAKING Filed March 11, 1953 Jan. 22, 1957 E. BRUEGGER 2 Sheets-Sheet 2 INVENTOR. Em esZ' Brae gum/41% ATTORNEYS 2,778,610 Patented Jan. 22, 1957 CATALYST FINNED TUBING AND METHOD OF MAKING Ernest Bruegger, Canal Fulton, Ohio, assignor to The.

Griscom-Russell Company, Massiilon, ()hio, a corporation of Delaware Application March 11, 1953, Serial No. 341,767 9 Claims. (or. 257-45219 This invention relates generally to heat exchanger apparatus and more particularly and specifically to finned tubing for a heat exchanger having fins coated with a selected catalyst and to a method of making catalyst coated finned tubing.

Prior heat exchanger tubing constructions have included various forms of projecting fins for the purpose of increasing the heat transfer area of the tubing and thereby incrementing the heat transfer between mediums passing within and around such tubing.

In certain prior constructions, fins of circular or helical form have been applied by various methods to heat ex changer tubing, while in certain other constructions fins of straight form have been applied, by various means, lengthwise or axially of the tubing. p

in these prior constructions such fins, circular, helical and axial, have been cast integrally with the tubing, soldered, welded or brazed to the tubing, secured in wedge shaped slots in the tubing Wall, or positioned in preformed grooves in the tubing and locked therein by rolling over or beading the grooves about a portion of the fins inserted therein.

While certain of these modes of fin attachment have been satisfactory for securing certain forms of fins to tubing for certain purposes and uses, none of thesemethods provides for securing catalyst coated fins to tubing which avoids damage to or contamination of the catalyst coating by such causes as tooling used or cooling mediums normally used incident to operations performed by tools for securing the fins to the tubing.

it is therefore a general object of the present invention to provide a catalyst coated finned tube construction and a method for making the same whereby it is possible to install, assemble and connect, in eflicient heat transfer relation, catalyst coated fins with tubing, without contaminating or damaging the catalyst by the tooling used for assembly, or by the cooling mediums normally required to be used with such tooling, or in any other manner.

Another prime object of this invention is the provision of a catalyst coated finned tube construction wherein the fins may be quickly and easily removed and replaced when desired or required. a I

An additional object of the instant invention lies in the provision of a catalyst coated finned tube construction in which there are no requirements for costly maintenance of close tolerances in manufacture, other than between the fin bases and the tubing grooves in which the fins are secured, since separate and positive tin holding andretaining means is utilized in the construction which permit of considerable variation in fin lengths, tensions, thicknesses, and the like.

It is another principal object of the present invention to provide a catalyst-coated, axially-finned tubing construction which has a maximum exposed heat transfer area providing maximum heat transfer efiiciency.

An additional object of the present invention is the struction and method of making the same which are adapted for production line manufacture at relatively low cost in terms of time, labor and equipment.

Still further it is an object of the present invention to provide a catalyst-coated finned tubing construction which is of simple and inexpensive design, and is highly efficient and durable in use.

These and other objects are accomplished by the parts, constructions, arrangements, elements, combinations, subcombinations, methods, steps and procedures which comprise the present invention, the nature of which is set forth in the following general statement, and preferred embodiments of which illustrative of the best modes in which applicant has contemplated applying the princip1es'are set forth in thefollowing description and illustrated in the accompanying drawings, and which are particularly and distinctly pointed out and set forth in the appended claims forming a part hereof.

In general terms the present invention may be stated as including an elongate heat exchanger tube, circumferentially spaced preferably wedge-shaped grooves extending axially of the outer surface of the tube, a plurality of elongate fin members frictionally preferably wedge-seated along the length of one edge thereof, one in each of said grooves to project radially from the tube, a catalyst coating covering the exposed areas of said fins, and compres sion bands or rings encircling the outer edges of said fins and compressively retaining the fins in said axial grooves; and wherein, in assembly, the fins are positioned at the open mouths of said wedge-shaped grooves, the compression rings are slidably positioned about the fin edges concentrically of the tube, and the rings are compressed, displaced, distorted or formed under pressure to force said fins into seated engagement in and to retain them in said grooves in efiicient heat transfer relation.

By way of example, embodiments of the improved catalyst-coated, axially-finned tubing and of the method of making such tubing are illustrated in the accompanying drawings forming a part hereof, wherein like numerals indicate similar parts throughout the several views, and in which:

Figure l is a side elevation of a portion of the improved tubing construction made by the novel method;

Fig. 2 is a vertical section taken on line 22, Fig. 1;

Fig. 3 is an enlarged sectional view illustrating the first stage in the new method of producing the instant novel construction;

tube;

provision of a catalyst-coated, axially-finned tubing co'n-' Fig. 7 is an enlarged fragmentary view of the first stage of the new method of starting the fin in the grooved tube; Fig. 8 is an enlarged fragmentary view of the final stage of the method of seating the fin in the grooved tube;

tions constituting the present invention and discovery. together with illustrative disclosure of methods by which such constructions may be manufactured.

' Structural assembly The finished structural assembly of the catalyst-coated finned tubing comprising the instant invention or disoovery, as is generally illustrated in Figs. 1 and 2, in.

3 cludes a length of typical heat exchanger tubing out to the length desired to form a tube for inclusion in a tube bundle and connection to tube sheets of a typical heat exchanger in the usual manner.

The tube 10 is provided in its outer surface with a plurality of preferably equally, circumferentially spaced grooves 11 formed axially of the tube. The grooves 11 are preferably, but not necessarily, formed in the tube by plowing or other like process which avoids the removal of metal so that the resultant grooves include a mouth portion defined by spaced raised beads 11a on the tube surface and inwardly tapering side walls 11b terminating in a bottom or base portion 11c of lesser lateral measurement than the lateral distance across the mouth opening of the groove. Thus the grooves 11 are somewhat wedge-shaped in cross-section.

A plurality of catalyst-coated fins 12 are positioned in radial projection about the tube with the base or root 13 of each fin inserted in the mouth of one of the grooves 11, and after assembly, the root of the fin is-held by means of compression rings 14 completely seated in its groove with intimate metal to metal contact providing for efficient heat transfer.

The compression rings 14 consist of continuous, hard metallic rings corrugated continuously thereabout as seen in end elevation in Fig. 2. The term ring as used hereinafter is intended to define either circular or polygonal rings or hands dependent upon the requirements of the construction and the outline configuration as defined by the fin peripheries.

The compression rings 14 are positioned concentrically about the tube 10 at spaced intervals along the length thereof with the ridge portions 16 of the corrugations of the ring engaging the outer extremities or edges of the fins 12, while the valley portions 17 of the corrugations are disposed centrally between the adjacent fins about the tube.

When the compression rings 14 have been applied to the tube and compressed, reformed, distorted or displaced inwardly thereof to seat the fins 12 in the grooves 11, the ridge portions 16 of the corrugations press radially inwardly against the outer edges 15 of the fins thereby securely holding the roots 13 of the fins seated in fixed engagement in the grooves 11.

Thus, the only surfaces of the fins which are contacted by the tube or the fin retaining ring means are the roots 13 of the fins which are inserted in the grooves 11 and the extreme outer edge portions of the fins which are in tensional engagement with the ridge portions 16 of the corrugated compression rings. By reason of this particular construction, the catalyst coating on the fin surfaces is not subjected to contact with any retaining structure which might tend to contaminate or damage the coating, nor is this coating subjected to any undue or unbalanced stresses which might tend to effectively damage it.

Further, the new construction maintains the maximum possible fin area in freely exposed condition so as to provide for and effect the maximum possible heat transfer between the fin surfaces and any heat transfer medium passing in contact therewith.

Referring to the construction shown in Fig. 10 wherein there is illustrated a circular tube 23 provided with circumferentially spaced grooves 24 about the outer surface thereof and extending axially thereof, typical catalyst coated fins 25 are seated and substantially retained in the grooves 24 by a wedge fit such as described hereinafter relative to the construction shown in Figs. 1 through 9. In this particular construction the fins 25 are suitably varied in length such as to make a substantially square or polygonal outline about the periphery of the fin as they project radially of the tube.

In the construction of such a tube having a fin periphery of polygonal configuration, a compression ring 26 of a substantially mating polygonal configuration is applied,

. 4 about the periphery of the fins and corrugated to compress the fin extremities within the ridges of the corrugations to retain the fins in their radially projected positions in a like manner to the fin retention by compression rings 14 in the construction illustrated in Figs. 1 and 2 and described above.

It is desirable that such a ploygonal fin periphery construction be provided since such arrangements of fins are desirable for the convenience of nesting tubes into a bundle and for providing a high rate of heat transfer in a small space.

Il Iethod of manufacture The three broad and basic stages in the method of making the catalyst-coated finned tube construction of Figs. 1 and 2, are generally illustrated in Figs. 3, 4 and 5 of the drawings.

At the outset, a section of heat exchanger tube 10 is provided with equally, circ umferent-ially spaced grooves 11 formed axially of the outer surface thereof by plowing or the like so as to provide grooves defined at the tube surface by longitudinal edge beads 11a and having inwardly tapering side walls 11b terminating in a base portion of lesser width than the lateral opening of the groove at the tube surface.

The spaced grooves 11 are formed with the wedgeshaped configuration above described in order that a tapered lock is effected for the root end of the fins as they are secured in the grooves. In order to attain a good locking fit it has been found that a side Wall taper for these grooves of from 2 to 4 is the most satisfactory since it provides the greatest locking characteristics with the minimum of tendency to squeeze the fins outwardly out of the groovesthe degree of taper for the grooves being exaggerated in the drawings for the purpose of clearer illustration.

In referring to the formation of the grooves 11 by plowing or the like, an operation is intended to be described in which tools closely resembling a snow or earth plow acting under pressure are used to form the grooves by a cold working operation during which the tool is moved along the length of the tube to throw up metal along its path displacing sufficient metal to form the groove and providing a raised bead 11a along the side edges of the groove as a result of the metal thrown upwardly by the plowing action. This groove forming operation is performed without metal loss in the tube Walls.

In the alternative, the grooves may be formed with any suitable cutting or planing tool to the desired wedgeshape and depth, but such operation will result in metal loss, and, accordingly, will not provide a raised bead at the edge of the groove to perform the additional gripping or clamping action on the root ends of the fins as is desired in the present constructions. Therefore, the plowing operation referred to above is preferred to a metal removal operation particularly in forming grooves in thin walled tubes where metal loss would be extremely undesirable.

Heat transfer fins 12 are formed to proper lengths from strips of the desired material of predetermined width and thickness. The fins are of substantially the same thickness as the lateral mouth opening of the grooves 11 at the tube surface. The fins 12 may be and preferably are coated with a selected catalyst such as 20, shown in Figs. 7 and 8.

The catalyst used to coat the fins may be any selected catalyst desired as a surface coating on the fins to pro mote some chemical reaction which may take place in fluids contacting the fins in a chamber surrounding the fins. Sometimes such chemical reaction may be exothermic in character and in such cases, the catalyst coating on the fins stimulates the reaction and the fin surfaces readily absorb the heat given off by the reaction.

; It is unnecessary in accordance with the present invention to maintain close tolerances in theywidth of the strip material used for forming the .fifls because the height of the fins may vary considerably from fin to fin without preventing proper assembly thereof to the tubes in view of the character of the spring-like compression rings 14 used for holding the fins assembled to the tubes.

Moreover, it is unnecessary to maintain close tolerances in the thickness of the fin strip material except at the root edges thereof since variations in fin thickness beyond the root of the fins has no effect on the assembly.

The first assembly stage in the method, generally illus trated in Fig. 3, is to locate the grooved tube 10, then to position the fins 12 in direct radial alignment with the grooves 11, as is generally indicated at 21, and then to initially move the fins radially inwardly of the tube to engage the fin roots 13 with the open mouths of the grooves 11, as is generally indicated at 22.

When all of the fins have been positioned with their roots 13 engaged in the grooves 11, preferably preformed, corrugated metallic compression rings 14 having ridges 16 and valleys 17 are slipped over the tube and associated fins to position the corrugation ridges 16 in direct radial alignment above each of said fins, as is best shown in Fig. 4. In this position, the corrugation ridges 16 are in close association with fin edges or extremities 15, being spaced only sufficiently therefrom to permit the ring to be slidably located over said fins longitudinally of the tube.

When the fins have been positioned and a compression ring 14 has been properly located about the tube and fins, as seen in Fig. 4, then pressure is applied, simultaneously and evenly, to all ridge portions 16 entirely about the ring on the outer ring surface at points indicated generally at A. This pressure application causes the fins to move radially inwardly to securely wedgeseat the roots 13 thereof in the grooves 11, as is seen in Fig. 5. At the same time, the ring formation is defiected to position the ridge portions 16 of the corrugation in tight engagement with the fin extremities 15.

Simultaneously with the application of pressure to the corrugation ridges 16, or in a step subsequent thereto, pressure is uniformly applied at B in the valley portions 7 about the compression ring to deform the ring valleys 1'7 to final shape 18 and to uniformly tension the ring about and against the fin extremities to permanently and securely position and lock the fins 12 in place.

Preferably, for ease of assembly of the compression rings 14 to the tube for seating and locking the fins in the tube grooves, the preformed compression rings 14 have an effective internal diameter such that the preformed rings may be slipped over a ring which has been seated and locked in the position indicated in Fig. 5.

Thus, when the first compression ring 14 has been applied to the tube adjacent one end thereof, the second ring to be applied may be telescoped over that end of the tube and pass over the previously aflixed ring for a predetermined distance therebeyond where it, in turn, is then secured by the same sequential operations above denoted relative to the first ring. This general method is repeated for each compression ring applied to the particular length of tube being constructed.

With reference to the modified compression ring construction 19, as illustrated in Fig. 9, there is shown a compression ring of true circular configuration, not preformed.

When using the modified compression ring construction 19 the ring is applied loosely about the fin extremities and located longitudinally of the tube, and then it is initially deformed by the application of pressure entirely about the tube and simultaneously against those portions of the ring immediately and radially aligned with the extremities of the fins, as generally designated at C.

The pressure at points C about the circular ring pushes the this downwardly into the grooves 11. and seats the fin roots 13 in the grooves 11. Then pressure is applied entirely about the tube at zones D to those portions of the ring which lie immediately outside of the spaces between adjacent fins in order to deform the ring into ridges and valleys and to permanently set those portions C of the ring, which become corrugation ridges, in tensional engagement with the extremities of the fins so that the ring will maintain the fins securely positioned and locked in the grooves 11.

In effect, the only modification in the method made necessary by the use of a non-preformed and truly circular compression ring as opposed to the use of a preformed partially corrugated ring 14 is the omission of the ring preforming operation.

While some of the catalyst coating on the fins 12 at theroots 13 thereof may be damaged or disturbed in wedge locking, the roots of the fins in the grooves 11 along the tapered groove side walls 11b, no catalystcoated areas of the fins which are exposed after final assembly are disturbed, since it is unnecessary to directly contact the fin surfaces with pressure tools during assembly or to use coolants for the assembly tools used. Although guide or spacer means which contact the fins may be incorporated in the tooling used to seat the fins in the grooves and to deform the compression rings 14, no coolants are required for the pressure tools used, and the pressure tools do not directly contact the fins.

In addition, a finned tube construction is provided for a catalyst finned tube 'of the type shown in Fig. 10 wherein the same general method steps may be used in manufacture as are above set forth with respect to the construction of the finned tube shown and illustrated in Figs. 1 and 2. However, where the periphery of the fins as applied to the tube defines a polygonal area, it is necessary to provide compression rings, either preformed with slight corrugations or of true polygonal configurations of the same general outline :and slightly greater area than the polygonal outline of the fin peripheries, to the tube peripheries Where they are compressed into corrugations much in the same manner as the compression of the ring 14 as applied to the construction illustrated in Figs. 1 and 2.

The particular method required for the construction of a tube of the type shown in Fig. 10, in each instance, necessitate the utilization of a specific means or apparatus for compressing the ring, dependent upon the dimensions and arrangements of the peripheral border defined by the fin extremities.

The present invention thus provides an improved cat alyst-coated finned tube construction which has inherent characteristics of good heat conductivity and dissipation, durability, simplicity and facility of design, and which may be inexpensively manufactured.

Furthermore, a finned tube construction is provided which permits the use of catalyst-coated fins without contamination of or damage to the catalyst during assembly by tooling operations used for assembly or by cooling liquids used in connection with such operations.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purpose herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, andthe scope of the present invention is not limited to the exact details of construction described or illustrated.

Having now described the invention, the construction,

use and manufacture of preferred embodiments thereof, and the advantageous, new and useful results obtained thereby; the new and useful constructions and methods, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

' I claim:

1. In heat exchanger apparatus, a tube, the tube having spaced longitudinal grooves for-med in its outer surface, longitudinally extending radially projecting fins having root edges held seated in said grooves, compression ring members peripherally surrounding the outer portions of said fins at spaced intervals longitudinally of said tube, the ring members being peripherally sinuous in shape with alternate ridges and valleys, the ridges engaging the 'outer portions of said fins, the valleys being located between adjacent fins radially inwardly of the outer fin portions, and the ring being tensioned to hold the fin root edges pressure-seated in said grooves.

2. In heat exchanger apparatus, an elongated tube, said tube having a plurality of grooves generally wedgeshaped in cross section spaced about and extending axially of the tube exterior, said grooves having inwardly tapering side walls extending from mouth openings to base portions of lesser width than the width of the mouth openings, a plurality of catalyst-coated fins having root edge portions approximately the same thickness as the width of said mouth openings and of greater thickness than the width of said base portions, said fin root edges being held wedge-engaged and seated one in each of said grooves, a plurality of compression rings peripherally surrounding the outer portions of said fins at spaced intervals longitudinally of said tube, the ring members being peripherally sinuous in shape with alternate ridges and valleys, the ridges engaging the outer portions of said fins, the valleys being located between adjacent fins radially inwardly of the outer fin portions, and the rings being tensioned to hold the fin root edges pressure-seated in said grooves.

3. In heat exchanger apparatus, a metal tube, the tube having spaced longitudinal grooves formed in its outer surface, the grooves being defined in cross section by spaced raised beads on the tube surface having side walls tapering inwardly toward each other and terminating in a bottom portion to provide a generally wedge-shaped cross section, a plurality of catalyst-coated metal fins having root edge portions approximately the same thickness as the width of the space between the raised beads at the outer edges of said tapered groove side walls and greater thickness than the width of said bottom portions, said fins being held seated with intimate metal-tomietal contact between the fin root edges and said tapered groove side Walls and bottom portion, and a plurality of compression ring members peripherally surrounding and permanently tensionally engaging the outer portions of said fins at spaced intervals longitudinally of said tube, the ring members being peripherally sinuous in shape with alternate ridges and valleys, the ridges engaging the outer portions of said fins, the valleys being located between adjacent fins radially inwardly of the outer fin portions, and the rings being tensioned to hold the fin root edges pressure-seated in said grooves.

4. The method of making axially finned heat exchanger tubing including the steps of forming axially extending grooves in the exterior surface of the tubing having inwardly tapered side walls extending from mouth openings to base portions of lesser width than the width of the mouth openings, positioning a plurality of fins in radial alignment with and engaged one in the mouth opening of groove, positioning a compression ring around the outer fin extremities; radially pressing portions of said ring against the outer fin extremities to move the fins radially inwardly in Wedge-seated engagement in said grooves; and radially pressing said ring between adjacent fins a greater distance radially inwardly than the outer fin extremities to compress, deform and permanently set said ring in permanent tensional engagement about the fin extremities thereby holding the fins seated in said grooves.

5. The method of making axially finned heat exchanger tubing including the steps of forming axial grooves having mouth openings in the exterior surface of the tubing, positioning a plurality of fins in radial alignment with and engaged in the mouth openings of the grooves, positioning a sinuous pressure ring in surrounding relation about the outer fin extremities; simultaneously radially pressing ridge portions of said ring against the outer fin extremities to move the fins radially inwardly in seated engagement in said grooves; and simultaneously radially pressing valley portions of said ring between adjacent fins a greater distance radially inwardly than the outer fin extremities to compress, deform and permanently set said ring in permanent tensional engagement about the fin extremities thereby holding the fins seated in said grooves.

6. The method of making axially finned heat exchanger tubing including the steps of forming axially extending grooves in the exterior surface of the tubing having inwardly tapered side walls extending from mouth openings to base portions of lesser width than the width of the mouth openings, positioning a plurality of fins in radial alignment with and engaged one in the mouth opening of each groove, positioning a sinuous pressure ring in surrounding relation about the outer fin extremities; simultaneously radially pressing ridge portions of said ring against the outer fin extremities to move the fins radially inwardly in wedge-seated engagement in said grooves; and radially pressing valley portions of said ring between adjacent fins a greater distance radially in wardly than the outer fin extremities to compress, deform and permanently set said ring in permanent tensional engagement about the fin extremities thereby holding the fins seated in said grooves.

7. The method of making axially finned heat exchanger tubing including the steps of forming axially extending grooves in the exterior surface of the tubing having inwardly tapered side walls extending from mouth openings to base portions of lesser width than the width of the mouth openings, positioning a plurality of fins in radial alignment with and engaged one in the mouth opening of each groove, positioning a sinuous pressure ring in surrounding relation about the outer fin extremities; applying pressure to the ridge portions of said ring and forcing said ring ridge portions against the tin extremities and moving the fins into the grooves in frictional wedge-seating and taper-locking position; and then applying pressure to the valley portions of said ring to deform the same a greater distance radially inwardly than the outer fin extremities to hold the ridge portions in permanent tensional engagement with the fin extremities about the tubing.

8. The method of making axially finned heat exchanger tubing including the steps of forming axial grooves in the exterior surface of the tubing, positioning a plurality of fins in said grooves, positioning a sinuous pressure ring in surrounding relation about the outer fin extremities; and simultaneously applying pressure to the ridge portions and the valley portions of the ling uniformly permanently tensioning the ring about and against the fin extremities and permanently and securely seating and locking the fins in place in said grooves.

9. The method of making axially finned heat exchanger tubing including the steps of forming axial grooves in the exterior surface of the tubing, positioning a plurality of fins in engagement with said grooves, positioning a first compression ring in surrounding relation about the outer fin extremities, deforming and permanently setting said first ring to radially decrease the outer dimensions thereof and hold it in permanent tensional engagement with the fin extremities about the tubing, telescoping other compression rings of approximately the same size as the first ring prior to deformation over said first permanently set ring, successively spaced from said first ring and each other, and successively deforming said other compression rings in place one at :a time in permanent tensional engagement with the fin extremities about the tubing.

References Cited in the file of this patent UNITED STATES PATENTS '10 Eldred Nov. 5, 1912 Wells Jan. 8, 1918 Guyer May 11, 1920 Kettering July 23, 1929 Martin Mar. 14, 1939 Zallea May 27, 1941 Litton Feb. 2, 1943 Bruegger Aug. 22, 1950 Simpelaar Nov. 2, 1954 

